- define checkstyle configs in as few places as possible
- use checkstyle:check since it has defaults that match what we want (fail after logging to console)
- modules that have current failures set property checkstyle.failOnViolation to false.

For reference, other bindings don't appear to specify a `groupId` at this level
in their `pom.xml` files.

@shivam-maharshi says in a [comment][1]:

> The groupId here is the duplicate of the parent groupId. This is creating a
> problem in the maven build.

  [1]: https://github.com/brianfrankcooper/YCSB/commit/d4b1d247a31cf9fbf42b2e324b5b1cc27fdd9565#commitcomment-15030853

The memcached support was extracted from PR #98 by @jbellis, with cleanups to
bring it in line with current APIs and style guide.

This PR also addresses issue #326.

Copyright statement, better exception messages, etc.

1. Move documentation from the properties file to the README.md
2. Addressed a couple of comments in the code.
3. Added the checkstyle plugin and addressed all the violation (except
the TODO comment violation. I'd like to keep a TODO item in the code).

[googledatastore] Output debug logs in one line instead of multiple lines.

Add a DB client for Google Cloud Datastore. This initial commit includes implementation of all CRUD operations (modulo scan), and integration into the rest of YCSB (pom.xml changes, etc)

Next few commits will include Scan/query support, single entity group support, and better documentation.

As a part of branching to stage 0.2.0 release in #266, set version
for continued development on master branch.

* remove unused declared deps in a few places
* lex sort modules in top level pom
* update maven plugin versions.
* no more jar-with-dependencies
* set ycsb-core to provided in bindings
* introduce a bindings-parent pom that sets
** stage dependency copy on building binding
** iff binding has a README.md, build a binding-specific dist artifact
* update distribution assembly to
** properly build after modules
** use per-binding sets of dependencies

closes #250

* Need a SNAPSHOT version because non-SNAPSHOT is reserved for actual releases.
* Increment minor version per pre-1.0 guidelines from the Version Numbers guide

Fixes #236.